<template>
  <div class="spec-preview">
    <img :src="skuImage.imgUrl"  />
    <div class="event" @mousemove="handler"></div>
    <div class="big">
      <img :src="skuImage.imgUrl" ref="big" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
     props:["skuInfo"],
    data(){
      return{
        currentIndex:0
      }
    },
    computed:{
      //这步骤很重要！！！否则会出现 Error in render: "TypeError: Cannot read properties of undefined (reading '0
      skuImageList(){
        return this.skuInfo.skuImageList||[]
      },
      skuImage(){
        return this.skuImageList[this.currentIndex] || {}
      }
    },
    methods:{
      handler(event){
       let mask=this.$refs.mask
       let big =this.$refs.big
       let x=event.offsetX-mask.offsetWidth/2
       if(x<0) x=0
       if(x>mask.offsetWidth) x=mask.offsetWidth
       let y=event.offsetY-mask.offsetHeight/2
       if(y<0) y=0
       if(y>mask.offsetHeight) y=mask.offsetHeight
       mask.style.left=x+"px"
       mask.style.top=y+'px'
       big.style.left=-2*x+"px"
       big.style.top=-2*y+"px"    
      },
    },
    beforeMount(){
      this.$bus.$on('changeBigImage',(index) =>{
        this.currentIndex=index
      })
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>